Interactions and effects of a stannous-containing sodium fluoride dentifrice on oral pathogens and the oral microbiome

Numerous studies have investigated the effects of stannous ions on specific microbes and their efficacy in reducing dental plaque. Nonetheless, our understanding of their impact on the oral microbiome is still a subject of ongoing exploration. Therefore, this study sought to evaluate the effects of a stannous-containing sodium fluoride dentifrice in comparison to a zinc-containing sodium fluoride dentifrice and a control group on intact, healthy oral biofilms. Utilizing the novel 2bRAD-M approach for species-resolved metagenomics, and FISH/CLSM with probes targeting periodontal and caries associated species alongside Sn2+ and Zn2+ ions, we collected and analyzed in situ biofilms from 15 generally healthy individuals with measurable dental plaque and treated the biofilms with dentifrices to elucidate variations in microbial distribution. Although significant shifts in the microbiome upon treatment were not observed, the use of a stannous-containing sodium fluoride dentifrice primarily led to an increase in health-associated commensal species and decrease in pathogenic species. Notably, FISH/CLSM analysis highlighted a marked reduction in representative species associated with periodontitis and caries following treatment with the use of a stannous-containing sodium fluoride dentifrice, as opposed to a zinc-containing sodium fluoride dentifrice and the control group. Additionally, Sn2+ specific intracellular imaging reflected the colocalization of Sn2+ ions with P. gingivalis but not with other species. In contrast, Zn2+ ions exhibited non-specific binding, thus suggesting that Sn2+ could exhibit selective binding toward pathogenic species. Altogether, our results demonstrate that stannous ions could help to maintain a healthy oral microbiome by preferentially targeting certain pathogenic bacteria to reverse dysbiosis and underscores the importance of the continual usage of such products as a preventive measure for oral diseases and the maintenance of health.

High sensitivity for detecting trace Sn2+ in canned food using novel covalent organic frameworks

Tin (Sn) element plays a vital role in the human body, and its detection is a mandatory inspection item for canned food. The application of covalent organic frameworks (COFs) in fluorescence detection has received extensive attentions. In this work, we designed a kind of novel COFs (COF-ETTA-DMTA) with high specific surface area (353.13 m²/g) by solvothermal synthesis using 2,5-dimethoxy-1,4-dialdehyde and tetra (4-aminophenyl) ethylene as precursors. It shows fast response time (about 50 s), low detection limit (228 nM) and good linearity (R² = 0.9968) for the detection of Sn²⁺. Via coordination behavior, the recognition mechanism of COFs toward Sn²⁺ was simulated and verified by the small molecule with the same functional unit. More importantly, this COFs was successfully applied to identify Sn²⁺ in solid canned food (luncheon pork, canned fish, canned red kidney beans) with satisfactory results. This work provides a new approach for determining metal ions with COFs taking the advantage of their natural rich reaction set and specific surface area, improving the detection sensitivity and capacity.

A coumarin-based fluorescent chemosensor as a Sn indicator and a fluorescent cellular imaging agent†

In the present study, fluorogenic coumarin-based probes (1–3) through condensation of 4-hydroxy coumarin with malondialdehyde bis(diethyl acetal)/triethyl orthoformate were prepared. The absorption and fluorescence emission properties of 2b and 3 in different solvents were studied, and a considerable solvatochromic effect was observed. The sensitivity of chemosensors 2b and 3 toward various cations and anions was investigated. It was revealed that compound 3 had a distinct selectivity toward Sn²⁺, possibly via a chelation enhanced quenching mechanism. The fluorescence signal was quenched over the concentration range of 6.6–120 μM, with an LOD value of 3.89 μM. The cytotoxicity evaluation of 3 against breast cancer cell lines demonstrated that the chemosensor was nontoxic and could be used successfully in cellular imaging. The probe responded to tin ions not only via fluorescence quenching, but also through colorimetric signal change. The change in optical properties was observed in ambient conditions and inside living cells.

A fluorogenic and colorimetric coumarin-based probe was synthesized and used for sensing Sn²⁺ inside and ouside of living cells.

Synthesis, characterization and potential sensing application of carbon dots synthesized via the hydrothermal treatment of cow milk

Carbon quantum dots (CQDs) were synthesized in this study by hydrothermally treating cow milk. The procedure is simple, non-hazardous to the environment, and does not necessitate the use of any special instruments or chemicals. CQDs were practically almost circular when they were manufactured and had an average size of 7 nm. Carbon (67.36%), oxygen (22.73%), and nitrogen (9.91%) comprised the majority of their composition. They feature broad excitation-emission spectra, excitation-dependent emission, and temperature-dependent photoluminescence. They remained quite stable in the presence of a lot of salt, UV radiation, and storage time. Because luminescence quenching mechanisms are sensitive to and selective for Sn²⁺, they can be employed to create a nanosensor for detecting Sn²⁺.

Highly Selective and Sensitive Ratiometric Detection of Sn2+ Ions Using NIR-Excited Rhodamine-B-Linked Upconversion Nanophosphors

Detection of Sn²⁺ ions in environmental and biological samples is essential owing to the toxicological risk posed by excess use tin worldwide. Herein, we have designed a nanoprobe involving upconversion nanophosphors linked with a rhodamine-based fluorophore, which is selectively sensitive to the presence of Sn²⁺ ions. Upon excitation with near-infrared (NIR) light, the green emission of the nanophosphor is reabsorbed by the fluorophore with an efficiency that varies directly with the concentration of the Sn²⁺ ions. We have explored this NIR-excited fluorescence resonance energy transfer (FRET) process for the quantitative and ratiometric detection of Sn²⁺ ions in an aqueous phase. We have observed an excellent linear correlation between the ratiometric emission signal variation and the Sn²⁺ ion concentration in the lower micromolar range. The detection limit of Sn²⁺ ions observed using our FRET-based nanoprobe is about 10 times lower than that observed using other colorimetric or fluorescence-based techniques. Due to the minimal autofluorescence and great penetration depth of NIR light, this method is ideally suited for the selective and ultrasensitive detection of Sn²⁺ ions in complex biological or environmental samples.

A handy and accessible tool for identification of Sn(II) in toothpaste

An easily accessible colorimetric probe, a carbazole-naphthaldehyde conjugate (CNP), was successfully prepared for the selective and sensitive recognition of Sn(II) in different commercially-available toothpaste and mouth wash samples. The binding mechanism of CNP for Sn2+ was confirmed by UV-Vis, 1H, and 13C NMR titrations. The proposed sensing mechanism was supported by quantum chemical calculations. Selective detection of Sn(II) in the nanomolar range (85 nM), among other interfering metal ions, makes it exclusive. Moreover, Sn2+ can be detected with a simple paper strip from toothpaste, which makes this method handy and easily accessible. The potential application of this system for monitoring Sn2+ can be used as an expedient tool for environmental and industrial purposes.

Fluorescent “OFF–ON” Sensors for the Detection of Sn2+ Ions Based on Amine-Functionalized Rhodamine 6G

These structurally isomeric rhodamine 6G-based amino derivatives are designed to detect Sn2+ ions. The receptors exhibit rapid fluorescent “turn-on” responses towards Sn2+. The absorption (530 nm) and fluorescent intensity (551 nm) of the receptors increase when increasing the concentration of Sn2+. The hydrazine derivative exhibits more rapid sensitivity towards Sn2+ than the ethylene diamine derivative, indicating that the presence of an alkyl chain in the diamine decreases the sensitivity of the receptors towards Sn2+. The presence of carbonyl groups and terminal amino groups strongly influences the sensitivity of the chemosensors toward Sn2+ by a spirolactam ring-opening mechanism. The receptors exhibit 1:1 complexation with Sn2+ as evidenced by Job plot, and the corresponding limit of detection was found to be 1.62 × 10−7 M. The fluorescence images of the receptors and their complexes reveal their potential applications for imaging of Sn2+ in real/online samples.

Rhodamine-based chemosensor for Sn2+ detection and its application in nanofibrous film and bioimaging

A simple rhodamine-based compound CK was designed and synthesized as a fluorescent chemosensor for Sn²⁺ based on Sn²⁺-mediated cyclization. The optical investigation indicated that the probe could quantitatively detect Sn²⁺ in a concentration range of 10-30 μM, with a detection limit of 118 nM. Moreover, probe CK, with low cytotoxicity, was successfully applied for imaging of Sn²⁺ in HeLa cells and mice, exhibiting excellent biocompatibility and cell membrane permeability. For on-site monitoring, CK-hybridized polymethyl methacrylate (PMMA) nanofibers were prepared by electrospinning and successfully employed for the visual detection of Sn²⁺ in actual samples. All the results demonstrated that the chemosensor could be a promising tool for the detection of Sn²⁺ in vitro and in vivo.

Recent advances in tin ion detection using fluorometric and colorimetric chemosensors

The innovation of chemosensors for tin ions (Sn4+/Sn2+) has evolved as a key research topic in recent decades, garnering a lot of attention due to their environmental, industrial and biological importance.

Easy and rapid chemosensing method for the identification of accumulated tin in algae: a strategy to protect a marine eco-system

A simple and potent chemosensor AFL has been successfully developed to recognize Sn2+ selectively in marine algae or, more precisely, seaweed, as they are at huge risk from marine contamination.

1-Adamantanamine-based triazole-appended organosilanes as chromogenic “naked-eye” and fluorogenic “turn-on” sensors for the highly selective detection of Sn2+ ions

1-Adamantanamine based organosilanes 4a–d have been synthesized and possessed selectivity towards Sn2+ ions only and serve as a colorimetric/fluorimetric dual-channel probe. The turn-on fluorescence has been marked on interaction with Sn2+ ions.

Preparation of a new fluorescence nanochemosensor for Sn(II) ions by a modified nanoprecipitation method

A new dialdehyde was designed and synthesized containing naphthalene groups, and then its macrocycle was prepared with 1,4-diaminobuthan. A modified nanoprecipitation method has been reported for the preparation of the nanoparticles. In this method, to obtain nanoparticles with small particle sizes, the nucleation rate was increased with decreasing of the mixing time. The organic nanoparticles were used for turn-off fluorescence response of low concentration of Sn²⁺ ions over cations such as Cs⁺, K⁺, Na⁺, Ba²⁺, Ca²⁺, Mg²⁺, Al³⁺, Pb^2+, Zn²⁺, Cu²⁺, Ni²⁺, Co²⁺, Fe²⁺, Mn²⁺, Ag⁺, Cd²⁺, and Hg²⁺ and ions in aqueous buffer solution. The limit of detection was 5.4 nM.

Retinal-based polyene fluorescent probe for selectively detection of Cu2+ in physiological saline and serum

Retinal is a flexible natural chromophore and widely present in organisms. The slender conjugated polyene structure retinal is conducive to entering protein structure. In this work, a novel turn-on fluorescent probe for Cu²⁺ based on retinal and phenylenediamine was designed and synthesized. The probe achieved recognition of copper ions in human serum complex protein environment. Furthermore, the high sensitivity, selectivity for Cu²⁺ and the sensing mechanism was also investigated.

A lysosome-locating and acidic pH-activatable fluorescent probe for visualizing endogenous H2O2 in lysosomes

We developed a lysosome-locating and acid-activatable fluorescent probe consisting of a H₂O₂-responsive boronate unit, a lysosome-locating morpholine group, and a pH-activatable benzorhodol fluorophore for the detection and visualization of H₂O₂ in lysosomes.

A through bond energy transfer based ratiometric probe for fluorescent imaging of Sn2+ ions in living cells

A 4-(naphthalen-1-ylethynyl) aniline appended rhodamine based fluorescent chemosensor ‘NAP-RD’ is synthesized which undergoes through bond energy transfer in the presence of Sn²⁺ ions in mixed aqueous media.

Sn(ii) induced concentration dependent dynamic to static excimer conversion of a conjugated naphthalene derivative

The colorimetric and fluorescence recognition of Sn²⁺ has been achieved using a naphthalene appended diformyl-p-cresol derivative (L). The dynamic excimer, observed up to 50 μM Sn²⁺, gradually converts to a static type above 50 μM Sn²⁺. DFT calculations support the experimental findings.